Slave-making ant
Slave-making ants are brood parasites that capture brood of other ant species to increase the worker force of their colony. After emerging in the slave-maker nest, slave workers work as if they were in their own colony, while parasite workers only concentrate on replenishing the labor force from neighboring host nests, a process called slave raiding. The slave-making ants are specialized to parasitize a single species or a group of related species, and they are often close relatives to their hosts, which is typical for social parasites. The slave-makers may either be permanent social parasites (thus depending on enslaved ants throughout their whole lives) or facultative slave-makers. The behavior is unusual among ants but has evolved several times independently. Terminology Theft of brood for the purpose of employing the stolen individual's efforts in support of the thief is called dulosis (from Greek doulos, "slave"), but the term "slave-making" is used in older literature and is still common.1 Herbers (2007) considered the term offensive and suggested that "slave-making ants" should be replaced with "pirate ants", noting that pirates take captives and rely on forced labor. Further, "slave" could be replaced with "captive" and "dulosis" with "leistic behavior" (Greek for pirated spoils, leistos).2 A related type of social parasitism is called inquilinism, in which a reproductive enters a host colony, lays eggs, and relies on the host colony to rear its offspring. Unlike brood parasitism, the inquiline remains within the nest and typically its brood does not outnumber the host's brood. Obligate and facultative slave-makers Slave-making ants may either be permanent social parasites, thus depending on enslaved hosts ants throughout their whole lives3 or facultative slave-makers. Facultative slave-making ants, like those in the Formica sanguinea complex, represent an intermediate parasitic group, between free-living species on the one hand, and obligatory slave-making species on the other. In laboratory tests, slaves were removed from colonies of Formica sanguinea and Polyergus rufescens. The behavior of F. sanguinea changed dramatically within 30 days of slave removal, with workers becoming self-sufficient at feeding and brood care. Workers of Polyergus, by contrast, were unable to care for their brood, and experienced high mortality. Raids Parasitized nests need to replenish the host workers periodically and this is achieved by raiding other nests in a process called slave raiding.35 The parasite workers are specialized for conducting raids in a two-step process. First, scouts individually search for potential host nests. When successful, the scout returns to its nest and recruits nest-mates to initiate the raid, during which slave-maker ants seize brood and bring it back home.6 A colony may capture 14,000 pupae in a single season.7 Most slave-raiders capture only brood, but Strongylognathus sp. also enslave adult workers.8 In most parasite species, workers mark the way to its nest with pheromones and afterwards fellow slave-makers are attracted in a few seconds. Then they go quickly to the targeted host nest, attack it, and carry as many larvae and pupae as possible and return to their nest following the same trail marked by the pheromone.5 Rossomyrmex is the only reported slave-maker that exclusively uses adult transport and single recruitment chain instead of pheromones during raids, a behavior probably constrained by the arid habitat: raids take place in early summer when soil surface temperature can reach up to 30 °C (86 °F), a temperature in which pheromones would quickly evaporate.5 Workers of the attacked nest can fight or flee. In the host species Proformica, the most common behavior is flight, probably because hosts almost always lose fights.5 Most studies on the raiding behavior of species in the F. sanguinea complex confirm that slave raiders usually rout their opponents, who typically flee in a state of panic alarm, and that aggressive encounters, when they occur, are brief and do not result in the death of adult individuals from either species. However, when large colonies of slave species offer resistance during raids, prolonged fighting is possible, and many workers of both species can be killed.9 Later, host workers emerging in the parasite nest will be imprinted on and integrated into the mixed colony where they rear the parasite brood, feed and groom the parasite workers, defend the nest against aliens, and even participate in raids,6 including raids against their original colony.10 Altruistic acts of slaves are thus directed toward unrelated individuals. One hypothesis suggests that slave deception is possible because slaves are captured as pupae and learn the slave-maker colony odor after emergence.11 However, in some cases, the enslaved ants rebel against their slave-maker ants, killing a large number of the slave-maker ant offspring.12 The reason behind this is because "slaves can gain indirect fitness benefits by reducing parasite pressure on nearby host colonies, because these are often closely related to the slaves".12 Thus, the slave ants protect their native colonies from further raids by slave-maker ants. Parasite–host pairs Category:Ants Category:Slave-making ants